Hitherto, heterostructure devices have been produced by liquid phase epitaxy (LPE) and by metal-organic chemical vapour deposition (MOCVD) growth techniques. It has been conventional practice to produce these devices by defining structure in preformed multi-layer structures.
Typical processes as aforesaid comprise:
(i) LPE or MOCVD growth of a multi-layered structure; followed by, PA1 (ii) Etch-resistant mask definition; PA1 (iii) Etch-definition of device structure; PA1 (iv) Staining to under cut active layer to reduce stripe width; PA1 (v) Infilling with semi-insulating or p-type doped material; and, PA1 (vi) Contact metallisation.
Process schedules for the above typically employ a large number of photolithographic mask definition stages and material selective etch process sequences. Furthermore, complex and expensive lithographic techniques are required for definition of sub-micron dimension structures.